[ccan] [PATCH 8/9] configurator: Pass output cflag to configurator

[Kevin Locke]

On 09/19/2016 11:23 PM, David Gibson wrote:
> On Sun, Sep 18, 2016 at 06:52:05PM -0600, Kevin Locke wrote:
>> Unfortunately, not all compilers support -o as a command-line option for
>> specifying the output file.  Visual Studio cl.exe issues warning D9035
>> when -o is given, which is detected as a compile warning by the
>> configurator.
>>
>> To support such compilers, pass the output flag as the last flag to the
>> configurator.
>>
>> This is a breaking change.  Existing scripts which pass flags to the
>> compiler must be modified to add "-o" as the last flag.  As noted in the
>> cover letter for this patch series, I'm open to considering alternatives
>> if this is unacceptable.
>
> So, as it stands, this change completely breaks ccanlint on POSIX,
> which is not ok.  Specifically it looks like the problem is that the
> DEFAULT_FLAGS from the configurator make it into CCAN_CFLAGS in
> config.h.  ccanlint then tries to add further options and its own -o
> to the end of that, which isn't going to work.
>
> In short, I think the problem is that ccanlint needs fixes to work
> with MSVC (and possibly anything much else apart from gcc).  I think
> we need to look at how to fix that and the configurator together with
> each other.
>
> Not having working ccanlint on Windows seems like a pretty big, since
> its the main tool for testing ccan, amongst other things.

Good catch.  I hadn't noticed the ccanlint breakage.  That was a big 
oversight on my part.

The breakage likely extends to any other programs which use CCAN_CFLAGS, 
since none are expecting the output flag at the end.  Perhaps a better 
solution would be to emit the output flag as a separate macro. 
Something like CCAN_OUTPUT_CFLAG.  What do you think?

The command line API for configurator could either expect the output 
flag to be the last argument as currently in the patch (which is a 
breaking change for anything which call it).  Or a command line option 
such as --output-cflag could be added to specify the flag and preserve 
command-line syntax compatibility.

Thoughts?

Kevin